In recent years, a hybrid vehicle is focused on as one type of vehicle of environment-friendly automobiles. The hybrid vehicle is generally provided, as power sources, with an internal combustion engine (hereinafter simply referred to as engine) powered by fuel such as gasoline or the like, and an electric motor (hereinafter simply referred to as motor) powered by electric power from a battery.
There is already developed an above mentioned type of a hybrid vehicle having mounted thereon a vehicle control apparatus comprising, for example, an engine, a motor, a clutch to engage or disengage the engine and the motor with each other, and a control unit (for example, refer to Patent Document 1). To start the engine of the type of the hybrid vehicle when the hybrid vehicle is being driven by the motor while the engine is not in operation, the vehicle control apparatus is adapted to engage a clutch to crank the engine by the motor.
To start the engine when the hybrid vehicle is being driven by the motor while the engine is not in operation, a torque that works as motor load is raised by the clutch being engaged to push-start the engine. For this reason, the rotational speed of the motor is sharply reduced even if the reduction is small, so that it is likely that there is generated a shock to prevent the vehicle from operating smoothly.
To suppress the vehicle from being prevented from operating smoothly by the shock, the control unit is adapted to calculate the amount of the load estimated to be increased in the motor by the push-start of the engine prior to engaging the clutch and to set the calculated amount of the load as a compensation torque of the motor. The control unit is further adapted to increase the output torque of the motor by the amount of the compensation torque at the timing of the engagement of the clutch. By the construction as set forth in above definition, generation of the shock due to the sharp increase of the motor load by the clutch being engaged is suppressed, thereby making it possible to start the engine while maintaining a smooth operation of the vehicle.
Meanwhile, as a result of diligent researches by inventors of the present invention, a fact was clarified that in this type of clutches there is some dispersion in property of each of clutches even among the clutches of the same kind due to errors in manufacturing and assembly by each of the clutches. To be more specific, as shown in a hatched region 100 in FIG. 10, there is some dispersion in timing of rise and amount in a torque at the engagement of each of the clutches (hereinafter simply referred to as clutch torque) even among the clutches of the same kind.
Within the dispersion range 100 of the clutch torque, each of the clutches takes its own unique rising line of the clutch torque 101. The rising line 101 of the clutch torque as shown in FIG. 10 is one example of the rising lines of clutch torque. Actually the rising line of the clutch torque is not limited to the rising line 101, but each of the clutches takes the rising line different from each other within the dispersion range 100 of the clutch torque.